One of the basic tenets of Neurosurgical planning is the ability to generate an operative approach that minimizes the disruption of normal tissues while allowing the required exposure of target tissues. To aid the surgeon in his or her ability to appreciate the location of target tissues, as well as their relationship to normal tissues, graphical workstation have been developed. The process of creating a patient specific 3- dimensional diagnostic dataset, provide the ability evaluate alternate surgical plans and the ability to apply the optimized virtual surgical plan to the real world patient at the time of surgery is termed image guided surgery. State of the art image guided surgery can be broken down into two broad categories, frame based guidance and frameless guidance. Each provides significant advantages and disadvantages when developing and carrying out a surgical plan. Disadvantages include frame application, the need for the frame to be present from initial imaging to the final portion of the procedure, the necessity of working with the frame in the operating room and the increase in operative time. For frameless image guidance the disadvantages include the potential inaccuracies in the patient to model registration as well problems and constraints imposed by the required 3-dimensional instrument tracking equipment. We are proposing a new guidance system that utilizes custom fabricated patient specific frame. This new frame creates the required alignment between the virtual patient model world and the actual patient at the time of surgery. As with routine framed or frameless image guidance a virtual surgical plan is developed. The surface of the patient is then derived from a 3-dimensional diagnostic dataset. This surface description allows the computation of a frame that precisely fits to he patient skin. This unique fit provides the geometric registration between the virtual 3-dimensional model of the patient and the real patient at the time of surgery. This registration permits the application of a virtual surgical plan to the patient at the time of surgery. The transfer of the virtual surgical plan is accomplished by including into the design of the custom patient specific frame the required alignment components. Biopsy holders, instructions regarding skin and bone incisions, skin clips, custom retractor design and retractor holders are all included into the design of the patient specific custom frame.